The special effects are sharper and the robots far more defined in Transformers: Age of Extinction.

Four films into the series, the giant thinking, wisecracking, lecturing alien robots finally have a look that suggests weight and metallic wear and tear.

Stanley Tucci and T.J. Miller provide human comic relief, and John Goodman and Ken Watanabe provide voices, sometimes used comedically, as a couple of new Autobots.

And, if Age of Extinction seems a silly indulgence, well, that’s the price of popcorn these days. If it keeps Michael Bay out of trouble for years at a time (this is the start of a new trilogy), we’ll just grit our teeth and bare it.

Five years since the Battle of Chicago, the Decepticons have been wiped out, their metal salvaged by a rich industrialist (Tucci).

But an alien robot bounty hunter named Lockdown has teamed with a rogue CIA megalomaniac (Kelsey Grammer) to try to wipe out or capture the last of the Autobots. All aliens must go.

Meanwhile, in rural Texas, inventor/scrap collector Cade Yeager (Mark Wahlberg) is trying to save the farm and his hotsy-totsy daughter’s virtue by salvaging a crashed semi. When he and his partner, Lucas (Miller), resurrect the old truck and it burbles to life as an outraged Optimus Prime (voiced by Peter Cullen, the luckiest man in show business), their world gets complicated — and deadly.

Middle age hasn’t dulled Bay’s passion for photographing nubile starlets from the midriff down. Thus does Nicola Peltz take on the Megan Fox role of Tessa, Yeager’s daughter. She spends the movie in heavy makeup and Daisy Dukes that Dad describes as “shrinking by the minute.”

Jack Reynor plays the beau whom high-school senior Tessa isn’t supposed to be dating. Luckily for everybody, the Irish-accented lad is a rally driver, and in the film’s best chase, saves father and daughter’s bacon hurtling through the Texas cornfields.

The humans and their gathered robot teammates crash from Texas to Chicago, Beijing to Hong Kong, transforming from souped-up cars into Autobots as they battle Lockdown’s metallic minions and trash assorted cities.

The wisecracks are pretty worn out by now. But Goodman, as a portly Autobot sergeant chomping an electronic cigar, spits out a few in between gunfights.

And gunfights are plentiful in the movie, resulting in a staggering, mostly unseen, body count. The language is rougher, but it’s the mayhem — much of it in the high-rise apartments and on the crowded streets, ferries and trains of Hong Kong — that boggles the mind.

Thousands must be dying as all of this real estate and transit is squashed. But we almost never see people, even in the Winnebago crushed during an interstate brawl.

Age of Extinction runs on and on in this manner. Two hours and 45 minutes is a pretty steep price to pay for keeping Michael Bay at bay.